This issue is likely a metadata problem with the underlying tables/fields which store the name of the record. A workflow variant of this issue is described by the following article:
http://teameasi.com/blog/crm-quick-search-not-returning-records-that-exist
I have experienced this issue (specifically on the workflow table) and the fix suggested by the author if this article (renaming the workflow) does work for me. I have also experienced similar issues in the past with contact records modified directly via SQL where the fullname field was not set correctly to reflect the underlying name fields.
Obviously this renaming approach is not particularly friendly for fixing a large number of records, I have some ideas for how to fix records in bulk which I will need to prove out.
Can you provide the following feedback:
- Try re-naming one of the affected contacts to see if this approach also works for the contact case?
- What version of CRM are you on, is it on-premise or online?
- Please test out whether you receive different results within the advanced find if you search based on the fullname field vs the firstname and lastname fields